A Langasite Crystal Microbalance Coated with Graphene Oxide-Platinum Nanocomposite as a Volatile Organic Compound Sensor: Detection and Discrimination Characteristics

We propose a novel langasite crystal microbalance (LCM) sensor with a graphene-based sensing medium to detect and discriminate volatile organic compounds (VOCs) at room temperature. A thin film of graphene oxide embedded with Pt nanostructures (GO-Pt nanocomposite) was deposited on the electrode surface of the LCM, a thickness-shear acoustic wave resonator. Ethyl acetate, acetic acid, and ethanol were chosen as typical VOCs for this study. Sensitivity and selectivity of coated LCM were investigated for different concentrations of the VOCs by analysing the resonant properties of the sensor. When exposed to VOCs, a negative shift in series resonance frequency was observed due to the mass loading of VOC molecules. Simultaneously, changes in equivalent resistance and parallel resonance frequency of the sensor were also observed due to the interaction of VOCs with charge carriers on the GO-Pt nanocomposite film surface. This dual measurement of both series and parallel resonance frequencies allowed for detection and discrimination of VOCs. Moreover, the high thermal stability of langasite makes the proposed sensor suitable even for harsh environmental conditions.

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An Efficient, Wideband, CPW-Fed Antenna Based on Simplified Composite Right/Left-Handed Transmission Line

Frequenz ◽

10.1515/freq-2016-0062 ◽

2017 ◽

Vol 71 (1-2) ◽

pp. 37-40

Author(s):

Zhaozhan Li ◽

Cheng Zhou ◽

Yanhong Lin

Keyword(s):

Transmission Line ◽

Resonance Frequency ◽

Dispersion Analysis ◽

Order Mode ◽

Electrically Small Antenna ◽

Left Handed ◽

Resonance Frequencies ◽

Unit Cells ◽

In Series ◽

Small Antenna

Abstract A wideband electrically small antenna (ESA) based on simplified composite right/left-handed transmission line (SCRLH-TL) is designed, fabricated and tested. The antenna consists of two different sized SCRLH-TL unit cells with different+1st-order mode resonance frequencies. The wideband property of antenna is achieved when these two+1st-order mode resonance frequency suitably merge. A dispersion analysis of the SCRLH-TL reveals that an increase in series of the dual-spiral capacitor would decrease the+1st-order mode resonance frequency, thus reducing the electrical size of the proposed antenna. The 10 dB fractional bandwidth (FBW10 dB) was 54.5 % and the measured maximum was 96.2 %, with an electrical size of 0.32λ0×0.16λ0×0.015λ0 at 3.0 GHz (where λ0 is the wavelength in vacuum). It is shown that the numerical results closely fit the measured results.

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Design and Optimization of the Dual-Mode Lamb Wave Resonator and Dual-Passband Filter

Micromachines ◽

10.3390/mi13010087 ◽

2022 ◽

Vol 13 (1) ◽

pp. 87

Author(s):

Tiancheng Luo ◽

Yan Liu ◽

Yang Zou ◽

Jie Zhou ◽

Wenjuan Liu ◽

...

Keyword(s):

Resonance Frequency ◽

Lamb Wave ◽

Piezoelectric Film ◽

Dual Mode ◽

Main Mode ◽

Rf Filters ◽

Design And Optimization ◽

Wave Resonator ◽

Passband Filter ◽

Resonance Frequencies

Radio frequency (RF) filters with multiple passbands can meet the needs of miniaturization and integration for 5G communications. This paper reports a dual-mode Lamb wave resonator (DLWR) and a dual-passband filter based on DLWRs. The DLWR consists of a piezoelectric film and two interdigital electrode (IDT) arrays with different thicknesses, which leads to the coexistence of two main modes in the resonator. The resonance frequencies of the two modes can be adjusted separately by changing the thicknesses of the IDTs, which greatly satisfies the requirements of the dual-passband filter. Four DLWRs with different electrode configurations are designed, and the influences of the periodic length and thicknesses of the IDTs on the performance of the DLWR are studied. When the thickness of the piezoelectric layer is 0.75 μm and the two thicknesses of the IDTs are 0.1 μm and 0.3 μm, the resonance frequency of the second main mode is 1.27 GHz higher than the resonance frequency of the first main mode in the DLWR. Furthermore, a dual-passband filter based on the proposed DLWRs is demonstrated with an insertion loss less than 1 dB and a band rejection of about 15 dB. Moreover, two passbands at 2.45 GHz and 3.88 GHz with bandwidths of 66 MHz and 112 MHz, respectively, are achieved. The presented DLWR shows a potential application that can be used to obtain RF filters with adjustable dual passbands.

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Disclosing the Sensitivity and Selectivity of Metal Oxide/Graphene Oxide-Based Chemoresistors towards VOCs

Engineering Proceedings ◽

10.3390/i3s2021dresden-10163 ◽

2021 ◽

Vol 6 (1) ◽

pp. 18

Author(s):

Eleonora Pargoletti ◽

Antonio Tricoli ◽

Mariangela Longhi ◽

Gian Luca Chiarello ◽

Giuseppe Cappelletti

Keyword(s):

Graphene Oxide ◽

Metal Oxide ◽

Uv Light ◽

Three Dimensional ◽

Polar Compounds ◽

Vital Role ◽

Oxide Semiconductors ◽

Dimensional Network ◽

Volatile Organic ◽

Sensitivity And Selectivity

Nowadays, gas sensors play a vital role in a plethora of applications. However, there are still some important shortcomings, such as the scarce selectivity and sensitivity, especially at low operating temperatures. Herein, we report the successful sensing achieved by tailoring the chemoresistive materials comprised of graphene oxide (GO) sheets well-integrated in a three-dimensional network of n-type metal oxide semiconductors (MOS). Thanks to the synergistic effect between GO and MOS under UV light, we obtained a very good sensitivity (down to 100 ppb) towards different volatile organic compounds (VOCs, i.e., ethanol, acetone, ethylbenzene, toluene) even at room temperature. Moreover, the best performing sensor (SnO2/GO 32:1) resulted in being highly selective towards polar compounds, such as acetone.

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Equivalent circuit for the characterization of the resonance mode in piezoelectric systems

Journal of Advanced Dielectrics ◽

10.1142/s2010135x15500320 ◽

2015 ◽

Vol 05 (04) ◽

pp. 1550032 ◽

Cited By ~ 1

Author(s):

Y. Fernández-Afonso ◽

O. García-Zaldívar ◽

F. Calderón-Piñar

Keyword(s):

Resonance Frequency ◽

Equivalent Circuit ◽

Low Frequency ◽

At Resonance ◽

Proposed Model ◽

Resonance Frequencies ◽

In Series ◽

Experimental Values ◽

Complex Manner

The impedance properties in polarized piezoelectric can be described by electric equivalent circuits. The classic circuit used in the literature to describe real systems is formed by one resistor (R), one inductance (L) and one capacitance C connected in series and one capacity ([Formula: see text]) connected in parallel with the formers. Nevertheless, the equation that describe the resonance and anti-resonance frequencies depends on a complex manner of R, L, C and [Formula: see text]. In this work is proposed a simpler model formed by one inductance (L) and one capacity (C) in series; one capacity ([Formula: see text]) in parallel; one resistor ([Formula: see text]) in parallel and one resistor ([Formula: see text]) in series with other components. Unlike the traditional circuit, the equivalent circuit elements in the proposed model can be simply determined by knowing the experimental values of the resonance frequency [Formula: see text], anti-resonance frequency [Formula: see text], impedance module at resonance frequency [Formula: see text], impedance module at anti-resonance frequency [Formula: see text] and low frequency capacitance [Formula: see text], without fitting the impedance experimental data to the obtained equation.

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Design and Analysis of a Novel Piezoceramic Stack-based Smart Aggregate

Sensors ◽

10.3390/s20226438 ◽

2020 ◽

Vol 20 (22) ◽

pp. 6438

Author(s):

Guangtao Lu ◽

Xin Zhu ◽

Tao Wang ◽

Zhiqiang Hao ◽

Bohai Tan

Keyword(s):

Resonance Frequency ◽

Electromechanical Coupling ◽

Structural Parameters ◽

Electromechanical Coupling Factor ◽

Coupling Factor ◽

Stress Waves ◽

Parallel Connection ◽

Smart Aggregate ◽

In Series ◽

Piezoelectric Wafers

A novel piezoceramic stack-based smart aggregate (PiSSA) with piezoceramic wafers in series or parallel connection is developed to increase the efficiency and output performance over the conventional smart aggregate with only one piezoelectric patch. Due to the improvement, PiSSA is suitable for situations where the stress waves easily attenuate. In PiSSA, the piezoelectric wafers are electrically connected in series or parallel, and three types of piezoelectric wafers with different electrode patterns are designed for easy connection. Based on the theory of piezo-elasticity, a simplified one-dimensional model is derived to study the electromechanical, transmitting and sensing performance of PiSSAs with the wafers in series and parallel connection, and the model was verified by experiments. The theoretical results reveal that the first resonance frequency of PiSSAs in series and parallel decreases as the number or thickness of the PZT wafers increases, and the first electromechanical coupling factor increases firstly and then decrease gradually as the number or thickness increases. The results also show that both the first resonance frequency and the first electromechanical coupling factor of PiSSA in series and parallel change no more than 0.87% as the Young’s modulus of the epoxy increases from 0.5 to 1.5 times 3.2 GPa, which is helpful for the fabrication of PiSSAs. In addition, the displacement output of PiSSAs in parallel is about 2.18–22.49 times that in series at 1–50 kHz, while the voltage output of PiSSAs in parallel is much less than that in parallel, which indicates that PiSSA in parallel is much more suitable for working as an actuator to excite stress waves and PiSSA in series is suitable for working as a sensor to detect the waves. All the results demonstrate that the connecting type, number and thickness of the PZT wafers should be carefully selected to increase the efficiency and output of PiSSA actuators and sensors. This study contributes to providing a method to investigate the characteristics and optimize the structural parameters of the proposed PiSSAs.

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Graphene quantum dots supported by graphene oxide as a sensitive fluorescence nanosensor for cytochrome c detection and intracellular imaging

Journal of Materials Chemistry B ◽

10.1039/c7tb01629h ◽

2017 ◽

Vol 5 (31) ◽

pp. 6300-6306 ◽

Cited By ~ 13

Author(s):

Lin Cao ◽

Xiangqing Li ◽

Lixia Qin ◽

Shi-Zhao Kang ◽

Guodong Li

Keyword(s):

Quantum Dots ◽

Graphene Oxide ◽

Cytochrome C ◽

Graphene Quantum Dots ◽

A549 Cells ◽

High Sensitivity ◽

Fluorescence Sensor ◽

Intracellular Imaging ◽

New Class ◽

Sensitivity And Selectivity

A new class of Cyt c detection fluorescence sensor based on graphene quantum dots supported by graphene oxide has been facilely developed. The sensor shows a high sensitivity and selectivity for Cyt c detection, and further exhibits favorable intracellular imaging in A549 cells.

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Study on the applicability of the microtremor HVSR method to support seismic microzonation in the town of Idrija (W Slovenia)

Natural Hazards and Earth System Science ◽

10.5194/nhess-17-925-2017 ◽

2017 ◽

Vol 17 (6) ◽

pp. 925-937 ◽

Cited By ~ 9

Author(s):

Andrej Gosar

Keyword(s):

Seismic Hazard ◽

Resonance Frequency ◽

Complex Geometry ◽

Free Field ◽

Seismic Microzonation ◽

Clear Correlation ◽

S Wave ◽

Resonance Frequencies ◽

Hvsr Method ◽

The Town

Abstract. The town of Idrija is located in an area with an increased seismic hazard in W Slovenia and is partly built on alluvial sediments or artificial mining and smelting deposits which can amplify seismic ground motion. There is a need to prepare a comprehensive seismic microzonation in the near future to support seismic hazard and risk assessment. To study the applicability of the microtremor horizontal-to-vertical spectral ratio (HVSR) method for this purpose, 70 free-field microtremor measurements were performed in a town area of 0.8 km2 with 50–200 m spacing between the points. The HVSR analysis has shown that it is possible to derive the sediments' resonance frequency at 48 points. With the remaining one third of the measurements, nearly flat HVSR curves were obtained, indicating a small or negligible impedance contrast with the seismological bedrock. The isofrequency (a range of 2.5–19.5 Hz) and the HVSR peak amplitude (a range of 3–6, with a few larger values) maps were prepared using the natural neighbor interpolation algorithm and compared with the geological map and the map of artificial deposits. Surprisingly no clear correlation was found between the distribution of resonance frequencies or peak amplitudes and the known extent of the supposed soft sediments or deposits. This can be explained by relatively well-compacted and rather stiff deposits and the complex geometry of sedimentary bodies. However, at several individual locations it was possible to correlate the shape and amplitude of the HVSR curve with the known geological structure and prominent site effects were established in different places. In given conditions (very limited free space and a high level of noise) it would be difficult to perform an active seismic refraction or MASW measurements to investigate the S-wave velocity profiles and the thickness of sediments in detail, which would be representative enough for microzonation purposes. The importance of the microtremor method is therefore even greater, because it enables a direct estimation of the resonance frequency without knowing the internal structure and physical properties of the shallow subsurface. The results of this study can be directly used in analyses of the possible occurrence of soil–structure resonance of individual buildings, including important cultural heritage mining and other structures protected by UNESCO. Another application of the derived free-field isofrequency map is to support soil classification according to the recent trends in building codes and to calibrate Vs profiles obtained from the microtremor array or geophysical measurements.

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Surface acoustic wave resonator from thick MOVPE-grown layers of GaN(0001) on sapphire

MRS Proceedings ◽

10.1557/proc-743-l6.37 ◽

2002 ◽

Vol 743 ◽

Cited By ~ 4

Author(s):

Sverre V. Pettersen ◽

Thomas Tybell ◽

Arne Rønnekleiv ◽

Stig Rooth ◽

Veit Schwegler ◽

...

Keyword(s):

Acoustic Wave ◽

Surface Acoustic Wave ◽

Electromechanical Coupling ◽

Film Surface ◽

Center Frequency ◽

Electromechanical Coupling Coefficient ◽

Nitride Film ◽

Wave Resonator ◽

Lift Off ◽

Definition Of

ABSTRACTWe report on fabrication and measurement of a surface acoustic wave resonator prepared on ∼10m thick GaN(0001) films. The films were grown by metal-organic vapor phase epitaxy on a c-plane sapphire substrate. The surface morphology of the films were examined with scanning electron and atomic force microscopy. A metallic bilayer of Al/Ti was subsequently evaporated on the nitride film surface. Definition of the resonator interdigital transducers, designed for a wavelength of λ=7.76m, was accomplished with standard UV lithography and lift-off. S-parameter measurements showed a resonator center frequency f0=495MHz at room temperature, corresponding to a surface acoustic wave velocity of 3844m/s. The insertion loss at center frequency was measured at 8.2dB, and the loaded Q-factor was estimated at 2200. Finally, measurements of the resonator center frequency for temperatures in the range 25–155°C showed a temperature coefficient of -18ppm/°C. The intrinsic GaN SAW velocity and electromechanical coupling coefficient were estimated at νSAW=383 1m/s and K2=1.8±0.4·10−3.

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